OONI : Open Observatory of Network Interference
T-Mobile USA Web Guard
Wed 21 Mar 2012
T-Mobile USA offers a “feature” to restrict access to certain kinds of content. This is called Web Guard. Supposedly Web Guard is supposed to inhibit access to content that falls under the following categories: Alcohol, Mature Content, Violence, Drugs, Pornography, Weapons, Gambling, Suicide, Guns, Hate, Tobacco, Ammunition.
By developing an OONI-probe test we were able to extract part of the list of censored content and discovered that sites that do not fall under these categories were also censored. This feature is enabled by default on all prepaid accounts and although it can be disabled by customers who wish to do so (if over 18 years of age), it is not clearly stated in the error page how to do so. This means that T-Mobile USA customers may be drawn into the Filternet without knowing how to get out.
How is the censorship performed?
The technique being used by T-Mobile USA to restrict access to certain content involves deploying a transprent HTTP proxy. This proxy intercepts every HTTP packet going through the network and checks it’s Host header field to see if it on the censored list. If the site is to be blocked it injects a fake response warning the user of the block. What this means is that the block is only effective against unencrypted HTTP traffic, but does not work for encrypted HTTPs traffic.
Some sites should not be censored
While most of the censored sites are legitimately categorized, there are certain ones that do not fall under the categories of the block. Here is a list of sites that we found to be censored, but that we don’t believe belong to any of the following categories Alcohol, Mature Content, Violence, Drugs, Pornography, Weapons, Gambling, Suicide, Guns, Hate, Tobacco, Ammunition.
The Tor Project is dedicated to proving anonymous secure communication
This is one of the most interestingly blocked website. Italy practices DNS based censorship for website that are related to online gambling. This is the block page is displayed when the IP address in the DNS response is spoofed. This is meta censorship!
The internet archive Way Back Machine. The Library of the Internet.
Newgrounds is an American entertainment and social media website. Wikipedia entry
Logical Media is an Affiliate Network.
Cosmopolitan is an international magazine for women. Wikipedia Article
Hide Refer hides the visitors HTTP refer from being seen by other websites
Chinese sports news website
French TV guide website.
Russian programming forum
French economics and financial news site
Chinese computer security website
9/11 conspiracy theory news site
Japanese URL shortening service
French funny news website
Website statistics collection site
Financial advice website
French website index
Polish sports news website
Chinese sports news website
Italian women advice website
Online Article directory
Sports news website
Estonian news portal
Greek political blog
Religious news site
Computer security Forum
French pop music hit list
What can we learn from this?
That if you are a Chinese sports fan or a French interested in economics under 18 you will have a hard time going with T-Mobile in the US. There appears to be overall a tendency to blocking foreign sports news websites.
When I asked T-Mobile US about the matter this is what came out with the following:
So T-Mobile is basically interfering into what should be taught by parents to their children. Since most of prepaid customers are under 18 they reserve the right to decide what is right and wrong for them, even bypassing their parents.
If I were a parent I would be mad that T-Mobile US chooses for my what my child should watch and should not.
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